1. Technical Field
The present invention concerns a seal especially for shafts movable in a translational direction having at least one static and at least one dynamic sealing area and another sealing point outside of the dynamic sealing area.
2. Related Art
In U.S. Pat. No. 3,563,556, a generic seal is described whereby the other sealing point provided outside of the dynamic sealing area is formed by a rubber element that lies on the shaft in its free end region and can move sideways in a substantially radial direction when the shaft is deflected in a translational direction in the manner of a bellows. Rubber elements of this type have a disadvantage in that, as a result of the constantly alternating shaft stroke in the area of deformation, forces are created that quickly cause the material to become brittle. The life of such a seal is therefore rather short. GB-A 621,526 describes a seal for rotating shafts. On the shaft-side, hydrodynamically activated slots are provided by which lubricants are prevented from seeping out. Additionally, a sealing element can be provided that is fixed to the shaft in a stationary position and that exhibits a sealing lip that is in contract with the top of an axial sidepiece exhibiting the hydrodynamic slots. This seal forms an additional rotating sealing point, by which any leaking lubricant can be retained.
It is the task of the present invention to improve on a generic seal in such a way that another sealing point can be formed outside the dynamic sealing area that no longer exhibits the disadvantages of the state of the art and that especially has a longer life than the state of the art according to U.S. Pat. No. 3,563,556.